Researchers with the ongoing Health, Aging and Body Composition Study (Health ABC) looked at the records of 2,038 elderly men and women to determine the amount of magnesium they were getting through foods and supplements, then measured their bone density using a scanning device called a fan-beam densitometer. They found that among white men and women, the more magnesium they took in, the denser their bones: “for every 100-milligram increase in magnesium, there was a 2 percent increase in bone density,” says lead author Kathryn Ryder, M.D., a physician at the University of Tennessee in Memphis, one of the study’s centers.
While that doesn’t sound like a lot, the researchers concluded that even small improvements in bone density can have a “major public health effect” in preventing debilitating bone fractures, since denser bones are stronger and less likely to break. No such relationship in magnesium intake and bone density was found among the African-American participants in the study.
Just how magnesium helps bones isn’t entirely clear, but the mineral seems to be vital in how the body uses calcium. “Magnesium might impact how the body’s hormones that regulate calcium are released and regulated—and maybe even how effective they are,” says Ryder. That African-Americans didn’t see as much bone benefit may be due to differences in those hormones, she suggests, “or other factors we weren’t able to tease out.”
But black or white, just about everyone could benefit from increasing their magnesium intake, since most people—including most Health ABC participants—don’t get enough. (People with kidney problems need to be cautious, however; “everyone should speak with their doctors before making a major dietary change,” says Ryder.)
How? Aim for 3 or 4 daily servings of low-fat dairy products if you can tolerate them, says Ryder, “since milk is a good source of both calcium and magnesium”—and get plenty of magnesium-rich foods like dark green vegetables, beans, avocados and nuts. If that’s not enough to put you in the recommended ranges [420 mg per day for men, 320 mg for women], she adds, “consider a calcium-plus-magnesium supplement if your doctor okays it.” Just don’t go overboard; experts consider 350 mg a safe upper limit for magnesium supplements.